The present invention relates to a valve rotator for rotating a valve of an internal combustion engine. The invention specifically relates to a type of valve rotator which uses a garter spring to rotate the valve.
Valve rotators which use a garter spring for rotating a valve of an internal combustion engine are known. U.S. Pat. Nos. 4,094,280; 3,537,325; 3,421,734 and 2,819,706 are examples of such rotators. A typical embodiment of a valve rotator using a garter spring includes a body attached to the valve. The body has an annular channel and a garter spring is longitudinally disposed within the annular channel. A spring washer acts between a collar and the body. The valve spring acts on the collar. When the valve is in a closed position, the coils of the garter spring are normally tilted relative to the axis of the garter spring due to side loading by the spring washer.
The principle of operation of the known garter spring valve rotators is simple. The spring washer acts against the valve rotator body and the frictional force therebetween resists rotation of the rotator body. As the valve opens, the valve spring is compressed between the collar and the cylinder head. The valve spring force is transmitted by the collar to one portion of the spring washer. The force the collar exerts on the spring washer causes the spring washer to deflect over the garter spring, increasing garter spring loading. The force of the valve spring is transmitted to the valve rotator body through the spring washer and the garter spring. As the side load on the coils of the garter spring increases, each coil of the garter spring will tilt further from its normal position. This action overcomes the frictional resistance between the spring washer and the body. Accordingly, the body and the valve rotate as the garter spring coils tilt, and the valve rotator body slides on the spring washer. As the valve closes, the spring washer restores itself to its valve-closed position, and the garter spring coils also restore themselves to their normal tilted position in preparation for another cycle.
In such rotators, the garter spring is subjected to oscillating loads and resonant frequencies induced by valve spring surges. Valve spring surges can cause garter spring failure in two ways. First, valve spring surge, while the valve is on its seat, can cause an unloading of the spring washer which engages the garter spring. This unloading can allow the garter spring coils to erect themselves. Specifically, the individual garter spring coils may lose their tilt or may tilt in different directions. When the spring washer subsequently loads the garter spring, the individual coils of the garter spring may be tilted in opposite directions. Second, longitudinal vibrations of the garter spring coils can be generated by valve spring surge. The longitudinal vibrations can cause relative movement of coils of the garter spring. Specifically, an end coil of the garter spring could move away from the other coils due to longitudinal vibrations. In fact, end coils have been known to move so far away from other coils that the end coils reverse or invert and subsequently break.
One solution is dislosed in U.S. Pat. No. 4,094,280. This patent discloses the use of a material which is placed in contact with the garter spring to dampen vibration of the garter spring. Another suggestion is to have a specially made garter spring whose coils are tilted in a free state as shown in U.S. Pat. No. 3,468,527. However, such has been difficult to manufacture.
The present invention is a totally new approach to solving the problems created by valve spring surge. The present invention minimizes the problem by isolating the garter spring from valve spring surges. In particular, the garter spring is isolated from surges which unload the valve spring and thus could unload the garter spring coils and create the aforementioned problems. Briefly stated, the invention consists of the inclusion of a specially constructed spring arrangement placed between the garter spring and the valve spring. The purpose and effect of the spring arrangement is to (i) isolate the garter spring from valve spring surges which would tend to excessively unload the garter spring and (ii) transmit the valve spring force to the garter spring when valve rotation is desired.
In accordance with the present invention, dual spring washers are located between the garter spring and the valve spring. One spring washer engages the garter spring. The other spring washer engages the first spring washer adjacent its inner periphery. The other spring washer at its outer periphery engages the collar against which the valve spring acts.
In one embodiment of the invention, when the valve is closed, the two spring washers are spaced apart at their outer periphery. Valve spring unloading results in unloading of the spring washer in engagement with the collar. Such unloading is not transmitted to the spring washer which engages the garter spring because of the space between the outer periphery of the two spring washers. However, when the valve spring force is increased, due to valve opening, the outer peripheries of the two spring washers move into contact, and force is transmitted to the garter spring coils to effect tilting thereof and rotation of the valve through both spring washers.
In accordance with another embodiment of the present invention, the outer peripheries of the dual spring washers may be in engagement when the valve is closed. In this embodiment, unloading of the valve spring a slight amount is not sufficient to result in disengagement of the spring washers. Thus, slight unloading of the valve spring is transmitted to the garter spring coils and thus reduces the side loading of the coils of the garter spring. However, excessive valve spring unloading causes the spring washers to separate at their outer peripheries before an excessive reduction in the side loading of the garter spring coils. Thus, excessive unloading of the garter spring coils does not occur.
In accordance with the present invention, the spring washers may be of a variety of different constructions. For example, one spring washer may be a conical washer, and the other may be a flat spring washer. Alternatively, both spring washers may be flat spring washers with a spacer between the inner peripheries thereof. Further, instead of a spacer between two flat spring washers, one of the washers may be provided with a lip which forms a spacer.
Further, the spring washers in the present invention may have a tendency to rotate about their own axes. Accordingly, the construction is made so that the spring washers are prevented from rotating about their own axes. This can be accomplished in a variety of ways, but preferably the spring washers are provided with flats which are engaged by a portion of the collar which encircles the spring washers to prevent rotation thereof.